The present invention relates to an apparatus and to a method for supporting a liquid sample for measuring an intensity of X-ray radiation scattered by the liquid sample. Further, the present invention relates to a system for measuring an intensity of X-ray radiation scattered by a liquid sample. In particular, the present invention relates to an apparatus and to a method for supporting a liquid sample for measuring an intensity of X-ray radiation scattered by the liquid sample, wherein the liquid sample is supported between two surfaces facing each other and supporting the liquid sample purely by a surface tension force. In particular, the electromagnetic radiation may be X-ray radiation, wherein, small angle X-ray scattering (SAXS), and/or wide angle X-ray scattering (WAXS) may be employed.
EP 1 477 796 A2 discloses a small angle X-ray scattering system with the X-ray beam oriented vertically for simplified analysis of liquid samples, wherein the sample is placed on a thin sample support, such as a piece of polyester film. Thereupon, the liquid sample is held and spreads naturally under the force of gravity.
The publication “High-Throughput Small Angle X-ray Scattering from Proteins in Solution Using a Microfluidic Front End”, Analytical Chemistry, 2008, 80, 3648-3654, by K. N. Toft et al. discloses a microfluidic system with sample and buffer inlets, mixing channel and sample chamber for measuring small angle X-ray scattering from a sample placed in the sample chamber. Thereby, the sample chamber comprises polystyrene (PS) enclosing the sample completely. An advantage of the microfluidic device employed in a scattering experiment may be that the sample conditions may be modified in situ. On the other hand, the surface to volume ratio is big resulting in a strong interference of a signal from the channel walls with a signal from the sample. In particular, the sample may be deposited or may sediment on the walls of the microfluidic device and may change the real concentration of the constituents of the sample (which may partially adhere to the channel walls of the microfluidic device). Moreover, in most cases filling of the channels requires pumping the fluid sample involving applying a shear stress to the sample. This may perturb or even damage especially a biological sample.
Alternatively, a liquid sample may be placed into a standard array of wells or of capillaries with an automatic sample changer for measuring X-ray scattering data. Typically, these automatic sample changers manipulate volumes of sample which are bigger than 1 μl or even bigger than 10 μl. Moreover, using syringes presents the same problems as the pumping of the sample when using microfluidic devices: The sample is subjected to shear stress with the risk of damaging or at least modifying the sample, in particular a sensible biological sample. Further, the true concentration of constituents, such as proteins, in the sample may be changed due to specific adsorption of specific constituents to a well wall or to a wall of a syringe.
There may be a need for an apparatus and for a method for supporting a liquid sample for measuring an intensity of X-ray radiation scattered by the liquid sample which allows very small sample volumes, such as in the microliter or nanoliter range, which reduces a contact area between a support and the sample, which reduces shear forces experienced by the sample, which reduces sample loss, which allows a fast measurement, which allows easy cleaning of the support and/or which allows easy coupling with an automatic sample changer.
Further, there may be a need for a system for measuring an intensity of X-ray radiation scattered by a liquid sample providing at least one of the above-mentioned advantages.